Gear finishing apparatus with a helix compensation

ABSTRACT

A gear finishing apparatus with helix compensation is disclosed, in which a helical gear is supported and rotated on a table by a gear holder and a tail stock, a finishing wheel is supported and rotated on a slider that can move toward and away from the finishing wheel in a substantially perpendicular direction to the gear axis, and the table and the slider are structured to relatively reciprocally move in the gear axis, wherein the gear holder comprises a drive motor for rotating a holder shaft for holding the helical gear; and a compensation drive unit by which a motor drum holding the drive motor is rotated about the gear axis, thereby compensating the circumferential speed in accordance with the helix angle of the helical gear during the relative movement of the helical gear and the finishing wheel in an axial direction of the gear and realizing high accuracy in the tooth profile of a helical gear.

FIELD OF THE INVENTION!

The present invention relates to a gear finishing apparatus forfinishing a helical gear by rotating an internally toothed finishingwheel with which the helical gear meshes.

PRIOR ART!

When high accuracy is required in the tooth profile of a gear, afinishing process, i.e., a so-called horning process is conducted tocorrect the deformation of the gear caused by a heat-treatment or thelike. The finishing process is performed by meshing a finishing wheelwith a workpiece gear at a predetermined crossed axes angle and thenrotating the workpiece gear to modify its tooth profile. The finishingwheel is of a gear shape (generally, an internally toothed gear) androtated by a drive unit. The finishing wheel moves in a directionperpendicular to the axis of the workpiece gear to cut in the workpiecegear. To perform a finishing process more uniformly, the workpiece gearis also moved repeatedly in an axial direction of the workpiece gear atthe cutting depth. When the workpiece gear is a spur gear, the workpiecegear has only to reciprocally move in an axial direction while rotatingat the same rotational speed as that of the finishing wheel, since thetooth surface of the workpiece gear is in parallel to its direction ofmovement. However, when the workpiece gear is a helical gear, the toothsurface thereof is inclined relative to its direction of movement.Therefore, the rotational speed of the finishing wheel needs to bemodified according to the helix angle of the helical gear in order toreciprocally move the workpiece gear substantially in a direction alongthe inclined tooth surface of the helical gear.

When rotatably attaching a helical gear on a tail stock and driving thehelical gear according to the rotation of the finishing wheel, thehelical gear is guided by the tooth surface of the finishing wheel andhas its rotation adjusted automatically by its helix angle in accordancewith the reciprocal movement of the workpiece gear in its axialdirection. However, to perform a more accurate finishing process, it ismore desirable to drive the workpiece gear at the same circumferentialspeed as that of the finishing wheel rather than to drive the workpiecegear by the finishing wheel. When finishing a spur gear, the workpiecegear has only to be driven at the same circumferential speed as that ofthe finishing wheel, since the direction of movement of the workpiecegear is in parallel to the tooth surface of the finishing plane asafore-mentioned. Actually, there has been a finishing machine thatperforms such an operation. However, as for helical gears, there hasbeen no such machine that drives a workpiece gear to accord with therotation of a finishing wheel. Therefore, the industry has been seekingsuch a machine.

PROBLEMS TO BE SOLVED BY THE INVENTION!

It is an object of the present invention to address these demands, i.e.,to provide a gear finishing apparatus that can perform a finishingprocess while driving a helical gear according to a finishing wheel.

MEANS FOR SOLVING THE PROBLEMS!

The object of the present invention is achieved by a gear finishingapparatus for finishing a helical gear by rotating a gear-type finishingwheel to thereby rotate the helical gear about its gear axis in meshwith the finishing wheel, the apparatus comprising:

a base;

a table supported on the base;

a gear holder supported on the table to hold the helical gear and rotatethe helical gear about its gear axis;

a tail stock supported by the table on the opposite side of the helicalgear to the gear holder to hold the helical gear;

a slider supported on the base so as to move toward and away from thehelical gear in a substantially perpendicular direction to the gear axisof the helical gear;

a finishing wheel holder supported by the slider and holding thefinishing wheel at a crossed axes angle relative to the helical gear androtatably about the central axis of the helical gear;

a finishing wheel drive unit for rotating the finishing wheel on thefinishing wheel holder; and

a feeder for moving at least one of the table and the slider forrelative movement between them in the direction along the gear axis,

wherein the gear holder comprises

a holder body supported on the table;

a holder shaft mounted on the holder body rotatably about the gear axisto hold the helical gear;

a drive motor for rotating the holder shaft;

a motor drum for holding the motor rotatably about the gear axisrelative to the holder body; and

a compensation drive unit for rotating the drum.

BRIEF DESCRIPTION OF THE DRAWINGS!

FIG. 1 is a front elevation of one embodiment of a gear finishingapparatus according to the present invention;

FIG. 2 is a plan view of the gear finishing apparatus show in FIG. 1;

FIG. 3 is a side view of the gear finishing apparatus of FIG. 1;

FIG. 4 is a front elevation of the gear finishing apparatus of FIG. 1 inoperation;

FIG. 5 is a vertical cross section showing the details of a gear holderof the finishing gear apparatus of FIG. 1; and

FIG. 6 is a cross section taken along Line VI--VI of FIG. 5.

EMBODIMENT!

The embodiment of the present invention will now be described below withreference to the accompanying drawings. FIGS. 1 and 2 are a frontelevation and a plan view of a gear finishing apparatus (out ofoperation) according to one embodiment of the present invention,respectively. This gear finishing apparatus comprises a bed-shaped base11 and a table 12 slidably supported on the base 11. The table 12 ismoved in right and left hand directions in FIGS. 1 and 2 by a feed motor13. Mounted on the table 12 are a tail stock 20 and a gear holder 30 forholding a workpiece gear. The tail stock 20 is of the typical type thatcomprises, at its fore end, a jig 22 for holding a workpiece gear, and acylinder 21, at its rear end, for advancing the jig to hold theworkpiece gear.

A gear holder 30 comprises a main body 31 disposed on the table 12. Thisgear holder will be later described.

Arranged on the rear of the base 10 is a slider 60. This slider 60 holdsa finishing wheel 50 above the table 12 and moves the finishing wheelperpendicularly to the axis of the tail stock to perform a cuttingoperation using the finishing wheel. The slider 60, for this purpose,comprises a slider body 62 disposed on a stationary base 61, the sliderbody 62 being driven by a slider motor 63 provided on the base 61 and afeed screw mechanism.

Provided on the fore end of the slider body 62 is a finishing wheelholder 70. The finishing wheel holder comprises an annular head 71 abovethe table 12. A wheel holder body 72 holds the head 71 rotatably aboutthe gear axis, and connects the head 71 to the slider body 62 of theslider. The head 71 is provided with external teeth and rotated by afinishing wheel drive motor 73 and a gear in mesh with the motor 73, themotor 73 being supported by the wheel holder body. On the innercircumferential surface of the head 71, a finishing wheel is securelymounted by attaching wheel retainer rings on either side of thefinishing wheel. The wheel holder body 72 is mounted on the slider body62 rotatably about the horizontal axis extending perpendicular to thegear axis, and is rotated about the horizontal axis by a gear mounted ona rotational shaft of the wheel holder body, a gear mounted on theslider body and a head turning motor 74 to thereby hold the finishingwheel at a desired crossed axes angle relative to the workpiece gear.FIG. 4 shows that a finishing wheel 50 is held at a desired crossed axesangle by the finishing wheel holder.

FIGS. 5 and 6 show the details of a gear holder. The gear holder 30comprises a main body 31 disposed on the table 12 and a motor 40accommodated in the main body.

The motor 40 comprises a spindle 41 at a location aligning with the axisof the tail stock, the spindle 41 being supported at its opposite endsby the main body 31. Mounted on the central portion of the spindle 41 isa coil, i.e., an armature 42. Further, in the main body 31, a motor drum43 is rotatably supported to surround the armature 42. Within the motordrum, a stator 44 is mounted to face the armature 42. The referencenumeral 45 of FIG. 5 denotes a roller bearing for rotatably supportingthe motor drum 43.

The fore end portion of the spindle 41 is of hollow cylindrical shapehaving an increased diameter and rotatably holds the rear end of aholder shaft 33 inside. Rotatably attached at the foremost end portionof the spindle 41 are three clutch pawls 34 that can take a position fortightly contacting the holder shaft and a position out of the contact,based on hydraulic power transmitted via an internal passageway throughthe spindle. A worm gear 35 is secured on the rear end portion of themotor drum 43. The main body 31 is provided with a worm 36 in mesh withthe worm gear. The shaft of the worm is connected to a helixcompensation motor 37 mounted on the main body 31. Provided on the rearportion of the spindle 41 is an encoder 46 for measuring the rotationalrate of the spindle. The output therefrom is sent to a controller.

The fore end of the holder shaft 33 receives one end of a work arbor onwhich the helical gear is mounted, and the cylinder 21 of the tail stock20 is pressed against the other end of the work arbor to hold thehelical gear at a working position.

The finishing gear apparatus operates as follows. Firstly, a finishingwheel 50 is attached to the head 71, which is then inclined at apredetermined crossed axes angle by the slider 60 and locked to meshwith a workpiece gear with a backlash. The helical gear A to be finishedis mounted on the gear holder 30 via a work arbor. Then, the jig 22 isadvanced by the cylinder 21 of the tail stock 20 to hold the helicalgear. At this time, the clutch pawls 34 are in a position out of contactwith the holder shaft. In this state, a finishing wheel drive motor 73and a gear drive motor 40 of the workpiece gear holder 30 are rotated.When it is detected via an encoder of the wheel drive motor 73 and theencoder 46 of the spindle detect that both motors have reached apredetermined rotational ratio, the clutch pawl is rotated by hydraulicpower to tightly contact holder shaft 33. Thereby, the finishing wheeland the helical gear are both driven and rotated at the samecircumferential speed. In this state, the feed motor 13 is actuated toreciprocally move the table 12 together with the helical gear in theaxial direction of the gear relative to the finishing wheel holder 70.In association with this reciprocal movement, the helix compensationmotor is actuated to rotate the motor drum 43 via the worm 36 and theworm gear 35. The rotation of the motor drum 43 is transmitted to theholder shaft 33 via the spindle 41. A controller of the helixcompensation motor 37 is programed, beforehand, to be controlled inrespect of the rotational speed and the amount of rotation in relationto the rotational rates of the feed motor 13 and the wheel drive motor73 and helix angle of the helical gear. In other words, as the helicalgear and the finishing wheel moves relatively to each other along thedirection of the gear axis, the rotational rates thereof are adjustedsuch that the tooth of the finishing wheel moves along the tooth surfaceof the helical gear. After the completion of the finishing process, areverse operation to the afore-mentioned process is conducted. Thehelical gear is lastly taken out from the gear holder 30.

In the above embodiment, an internally toothed finishing wheel was used,but it is also possible to use an externally toothed finishing wheel. Inthis case, the above-mentioned basic structure is employed, for example,the finishing wheel can be rotated in mesh with the workpiece gear at apredetermined crossed axes angle. Further, the finishing wheel isrotated by a wheel drive motor via a transmission mechanism made up ofgears that rotates with the finishing wheel.

ADVANTAGES OF THE INVENTION!

As described above, according to the present invention, the holder shaftof the gear holder is driven and rotated by a motor built in the holderbody of the gear holder, in addition to a drive unit for rotating thefinishing wheel. Further, the gear holder comprises a rotational driveunit for rotating a motor drum of a motor built therein, so that thebuilt-in motor can be rotated with the gear holder shaft. Therefore,when the workpiece gear is reciprocally moved along the gear axis in afinishing process, the holder shaft can be rotated by the motor inrelation to the reciprocal movement. Thereby, even if the tooth surfaceof the finishing wheel is inclined relative to the direction ofreciprocal movement of the workpiece gear, it is possible toreciprocally move the teeth of the helical gear along the tooth surfaceof the finishing wheel while rotating the helical gear. As a result, itis possible to perform a high-accurate finishing process by driving boththe finishing wheel and the helical gear.

We claim:
 1. A gear finishing apparatus for finishing a helical gear byrotating a gear-type finishing wheel to thereby rotate the helical gearabout its gear axis in mesh with the finishing wheel, the apparatuscomprising:a base; a table supported on the base; a gear holdersupported on the table to hold the helical gear and rotate the helicalgear about its gear axis; a tail stock supported by the table on theopposite side of the helical gear to the gear holder to hold the helicalgear; a slider supported on the base so as to move toward and away fromthe helical gear in a substantially perpendicular direction to the gearaxis of the helical gear; a finishing wheel holder supported by theslider and holding the finishing wheel at a crossed axes angle relativeto the helical gear and rotatably about the central axis of the helicalgear; a finishing wheel drive unit for rotating the finishing wheel onthe finishing wheel holder; and a feeder for moving at least one of thetable and the slider for relative movement between them in the directionalong the gear axis, wherein the gear holder comprises:a holder bodysupported on the table; a holder shaft mounted on the holder bodyrotatably about the gear axis to hold the helical gear; a drive motorfor rotating the holder shaft; a motor drum for holding the motorrotatably about the gear axis relative to the holder body; and acompensation drive unit for rotating the drum.
 2. A gear finishingapparatus according to claim 1, wherein the drive motor of the gearholder rotates the helical gear at the same circumferential speed as thefinishing wheel rotation caused by the finishing wheel drive unit.
 3. Agear finishing apparatus according to claim 1, wherein the compensationdrive unit moves forwards and backward the rotational phase of the motordrum to accommodate the rotational phase to a helix angle of the helicalgear during the relative reciprocal movement of the table and the slidercaused by the feeder so that the reciprocal movement is carried outalong with the tooth surface of the helical gear during rotation of thefinishing wheel drive unit and the gear drive motor.